Unfortunately, this is something it seems few doctors discuss. A shame, since this is an important question for others, even if not gay.
Anyway, I am not sure there is a strict rule, and it probably depends on a lot of factors. But, basically, yes anal intercourse is possible, but for all the reasons you can imagine, it can be risky. You don't know if you have an anal stricture, or if your pouch is quite short, or other limitations. The structure of the ileum is different than the rectum, which is much more elastic and distendable. The rectum also has thicker walls, so is more durable.
Yeah, talk to Eric. He has a k-pouch now, bot had a j-pouch for a number of years.